LASER CYTOMETRIC ANALYSIS OF PERMETHRIN TOXICITY IN INSECT AND MAMMALIAN EPITHELIAL CELLS

Insect epithelial cell lines derived from Anopheles gambiae and Aedes albopictus mosquito larvae and a clonal rat liver cell line (Clone 9) were exposed to the synthetic pyrethroid insecticide permethrin. There is ample evidence that permethrin acts primarily on nerve cells by modulating voltage-activated sodium channels, but little is known of its possible effects on nonexcitable cells. In this study, endpoints of cellular injury in epithelial cell lines were evaluated by laser cytometry. Kinetic analyses of intracellular glutathione, intracellular Ca2+ content, reactive oxygen species production, mitochondrial and plasma membrane potentials, intracellular pH, and gap junctional intercellular communication were performed. The permethrin concentrations that resulted in 50% inhibition of cell proliferation at 72 h (IC50) for Anopheles gambiae and Aedes albopictus cells were 15 n M and 300 n M , respectively. The rat Clone 9 cells did not show any growth inhibition when treated with permethrin even at the highest concentration used (10 uM ). Anopheles gambiae cells treated at the IC50 concentration for 1 h at room temperature exhibited changes only in the plasma membrane potential values, indicating toxin-induced sustained depolarization. However, when Aedes albopictus cells were treated with permethrin at the IC50 and Clone 9 cells were treated at a concentration of 1.0 uM for 1 h, elevation of reactive oxygen species, depolarization of mitochondria, and suppression of glutathione levels were observed. These studies identified possible cellular targets of injury in nonexcitable epithelial cells caused by exposure to permethrin and revealed that insect epithelial cells are much more sensitive to this toxin than mammalian epithelial cells. This report directly compares effects of a cytotoxin on insect and mammalian cells, and illustrates the potential of laser cytometry as a direct and rapid method of analyzing the effects of pesticides on living cells rather than on animals.